Cold-adapted bacteria primarily have two glucose 6-phosphate dehydrogenase isozymes (G6PD, also known as zwf), zwf-1 for the Entner–Doudoroff pathway and zwf-2 for the oxidative pentose phosphate pathway. Although the roles of zwfs in carbon metabolism and antioxidant defense have been reported, the biochemical properties of zwfs at low and moderate temperatures have not been fully described. In this study, we cloned and characterized zwf-1 (Pmzwf-1) and zwf-2 (Pmzwf-2) from a cold-adapted bacterium Pseudomonas mandelii JR-1. Pmzwf-1 and Pmzwf-2 were expressed in Escherichia coli BL21 (DE3) as soluble tetrameric proteins. Both Pmzwf proteins were active at 4 °C, but Pmzwf-1 exhibited overall better biochemical properties than those of Pmzwf-2, including 10–30% higher specific activity at 4–40 °C as well as consistent conformational flexibility and thermal stability in the 4–40 °C range. Pmzwf-2 showed reduced thermal stability at moderate temperatures. Furthermore, the mRNA expression of Pmzwf-1 was higher than that of Pmzwf-2 at both 4 °C and 25 °C. These results indicate that Pmzwfs are cold-adapted enzymes, but Pmzwf-1 can function at both low to moderate temperatures while Pmzwf-2 is primarily functional at low temperatures. Our results suggest distinct temperature adaptations of two G6PD isozymes in P. mandelii JR-1, adaptations that are metabolic pathway dependent.

中文翻译：

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冷适应曼氏假单胞菌的两种葡萄糖6-磷酸脱氢酶同工酶的生化比较。

冷适应细菌主要有两个葡萄糖-6-磷酸脱氢酶同工酶（G6PD，也被称为的zwf），ZWF-1为ED途径和ZWF-2用于氧化戊糖磷酸途径。尽管已经报道了zwfs在碳代谢和抗氧化防御中的作用，但是尚未充分描述zwfs在低温和中温下的生化特性。在这项研究中，我们从冷适应细菌曼氏假单胞菌JR-1中克隆并鉴定了zwf-1（Pmzwf-1）和zwf-2（Pmzwf-2）。Pmzwf-1和Pmzwf-2在大肠杆菌BL21（DE3）中表达为可溶性四聚体蛋白。两种Pmzwf蛋白都在4°C下有活性，但Pmzwf-1的总体生化特性比Pmzwf-2更好，包括在4-40°C时比活性高10–30％，并且在构象中具有一致的构象柔韧性和热稳定性。 4–40°C范围。Pmzwf-2在中等温度下显示出降低的热稳定性。此外，在4℃和25℃下，Pmzwf-1的mRNA表达均高于Pmzwf-2的mRNA表达。这些结果表明Pmzwfs是冷适应的酶，但Pmzwf-1可以在低温至中度温度下起作用，而Pmzwf-2则主要在低温下起作用。我们的结果表明曼氏疟原虫中两种G6PD同工酶的不同温度适应性 JR-1，依赖于代谢途径的适应。